A standard ring back tone is the “ring . . . ring” sound a person hears when placing a telephone call to another person before that other person answers the telephone. The ring back tone is a sound effect used to inform the person making the phone call that the connection towards the called device is being established and the called person is being alerted about the new incoming call.
A personalized ring back tone (PRBT) service lets a called party customize the ring back tone sound to anything of the called parties choosing. A personalized ring back tone service feature therefore enables a called party to play audio, such as a voice message, but also video or picture files, to a caller instead of the standard ring back tone when the called party is called by the specified caller.
The option of having a personalized ring back tone may be provided as a service for which a called party pays a nominal fee. Ring back tones are not stored on the telephone itself. Instead, ring back tones are stored on and played by a telephone network. As a result, they can be used with any telephone, including land line telephones, mobile telephones, Personal Digital Assistant (PDA) and Voice Over Internet Protocol (VoIP) communications devices.
Furthermore personalized ring back tones may be of an advanced sound quality approaching that of human speech. Therefore, a personalized ring back tone may include any file such as a song or voice recording, and may be of any type that the called party desires.
Because a personalized ring back tone may be customized by the called party for each individual caller, if caller A calls the called party, caller A may hear a specific unique personalized ring back tone that the called party has selected specifically for caller A. If caller B calls the called party, caller B may hear a different personalized ring back tone.
Call lists may be created by the called party, so that all of the callers belonging to one call list will hear the same personalized ring back tone and all other callers, or all callers belonging to a different call list will hear a different personalized ring back tone.
A personalized ring back tone can also be date, time, or location specific, meaning that caller A could receive one personalized ring back tone if he or she calls in the morning, on a particular day of the week, or from a particular location, and a different personalized ring back tone if he or she calls at a different time, day, or location.
The called party has complete control over exactly who hears which personalized ring back tone. As a result, a personalized ring back tone may be thought of as a personalized message selected by the called party that is automatically played to the selected caller or callers when a call is received, even if the called party never answers the telephone.
The personalized ring back tones may be stored as files in a database associated with a telephone network and may be retrieved with the assistance of a Gateway Mobile Switching Services Center (GMSC), in response to a call placed to a called party by a caller.
The Gateway Mobile Switching Services Center generally handles calls arriving from other networks and performs the switching of calls between mobile users and between mobile and fixed network users. This is what enables a land line or VoIP caller to hear a personalized ring back tone.
When the called party is under legal electronic surveillance by an authorized agency to monitor the called parties telephone conversation, the Mobile Switching Center (MSC) associated with the Gateway Mobile Services Switching Center is used as an intercept access point (IAP), and in-band signaling coming from the terminating Mobile Switching Center is intercepted. However, in-band signaling originating from the database associated with the network where personalized ring back tones are stored is not intercepted or monitored.
The personalized ring back tone, which originates from this database and not from the terminating Mobile Switching Center, is therefore not intercepted by currently available electronic monitoring systems. Therefore, the authorized agency implementing the electronic surveillance is not aware that a monitored called party is using personalized ring back tones to communicate with a caller.
Because the quality of personalized ring back tones may include normal sounding human speech, and because the called party may control which caller bears which personalized ring back tone, a problem arises in situations where a called party attempts to pass on communication to circumvent legal electronic surveillance methods.
For example, a law enforcement agency may be using electronic surveillance to monitor the telephone communications of the called party. This monitoring does not extend to either a ring back tone or a customized ring back tone. Therefore, a called party with criminal intent could use the personalized ring back tone to communicate messages to particular callers while avoiding legal electronic surveillance of the called party's telephone.
Such clandestine messages may be of a malevolent nature. For example, one may use this means of communication to relay a message regarding a planned criminal act. It is plain to see that personalized ring back tones may be used to covertly convey messages without the risk of electronic government surveillance to further the planning of common criminal acts, from drug dealing to conspiracy.
It is currently not possible to monitor a ring back tone or a personalized ring back tone for lawful interception purposes. An agency authorized to monitor a called party may be unaware that the called party is using a personalized ring back tone to send in-band information to specified callers. Since a warrant generally may be activated for data monitoring only, a personalized ring back tone may be lost if the agency authorized to monitor a called party is not aware that a personalized ring back tone is capable of communicating in a manner suitable for lawful interception purposes.